Norman Sleep, professor of geophysics at Stanford, will address the topic "Asteroid Impacts and the Evolution of Life on Earth versus Mars." Sleep's research suggests that Mars might actually have been a more hospitable place for life to evolve in the early days of the solar system than was Earth.

David Morrison, director of space at NASA Ames Research Center, will discuss various methods for "Protecting Earth from Asteroids." Earth has been struck by large asteroids many times in the past. Such collisions can generate energies many times greater than that released by hydrogen bombs. There is no question that the planet will be hit again and the only question is when. Morrison will discuss possible means of defense.

The symposium is sponsored by the NASA Ames Research Center and Stanford's Center for Space Science and Astrophysics.